Reduced Fitness of Daphnia magna Fed a Bt-Transgenic Maize Variety

Abstract

Genetically modified (GM) maize expressing the Bt-toxin Cry1Ab (Bt-maize) was tested for effects on survival, growth, and reproduction of the water flea Daphnia magna, a crustacean arthropod commonly used as a model organism in ecotoxicological studies. In three repeated experiments, D. magna were fed 100% ground maize in suspension, using either GM or isogenic unmodified (UM) maize. D. magna fed GM-maize showed a significantly reduced fitness performance: The mortality was higher, a lower proportion of females reached sexual maturation, and the overall egg production was lower compared to D. magna fed UM isogenic maize. We conclude that the tested variety of Bt-maize and its UM counterpart do not have the same quality as food sources for this widely used model organism. The combination of a reduced fitness performance combined with earlier onset of reproduction of D. magna fed Bt-maize indicates a toxic effect rather than a lower nutritional value of the GM-maize.

Notes

Acknowledgments

We would like to thank Dr. Chito Medina and farmers from the Iloilo district in the Philippines for providing the maize samples used in the experiments. We are grateful to Professor Kaare M. Nielsen for valuable discussions related to the experiments. We also thank Dr. Idun Grønsberg, Marte Albrigtsen, Julia Eggert, and Elisabeth Olsen at the GenØk Lab in Tromsø and Dr. Morten Johansen and Kriss Rokkan Iversen at the Norwegian College of Fishery Science for practical assistance during the experiments. The studies were supported by a grant (Project No. 154504) from the Research Council of Norway.